Mouthparts of honey bee worker (posterior view). After Michener (1974, fig. 1.6) [1]. The mouthparts are unfolded and spread apart. Most of the time they are folded behind the head and held together. See also mechanism of folding of the mouthparts.

Cd - cardo (plural cardines)
Ga - galea
Gls - glossa (tongue)
Lbl - labellum
LbPlp - labial palpus
Lr - lorum [2], submentum [1]
MxPlp - maxillary palpus
Pgl - paraglossa
Pmt - postmentum [2], mentum [1]
Prmt - prementum
St - stipes

The glossa is similar to a long cylinder. The diameter of the glossa is 185.0±1.5 micrometers at the base and 96.6±0.3 micrometers in the middle part. The glossa consists of segments. Length of one segment is about 23 micrometers. On apical part of each of the segments there are 16-20 hairs. The hairs on basal part of the glossa are stiff and short (32 - 63 micrometers long), whereas the hairs on the middle and apical part are longer (171.9±0.3 micrometers long) [3]. At the apex of the glossa there is a spoon-like flabellum. The mouthparts are cleaned with foreleg tarsi [4].

Ingesting liquid food by bees is based on mechanism of "viscous dipping" [5]. The tongue is extended and immersed into nectar. At this stage hairs on the glossa erect asynchronously [6][7] and trap the nectar [8], see also video [5]. The erectable hairs can increase the ability of a bee to collect nectar [3]. Next, when coated with nectar, the glossa is retracted to a tube formed from galeae and labial palpi. Then the nectar is sucked into pharynx. There are ridges on the inner wall of galeae which can reduce friction during drinking [9][10]. Honey bees are able to imbibe 1.8 microlitres of diluted nectar per second [11]. This rate is lower in case of higher concentrations of nectar [11]. It was suggested that the optimal for bees concentration of sugar in nectar, which is a compromise between energy content and intake speed is about 52% [5] but see [3]. There are sensory organs on the mouthparts which facilitate the food intake [12][13][14][15].

References